LARGE CAPACITANCE ELECTRIC DOUBLE-LAYER CAPACITOR USING ACTIVATED CARBON-CARBON COMPOSITE

An electric double layer capacitor with large capacitance, 1000 F at 5.5 V, has been developed. It uses activated carbon/carbon (AC/C) composite as the polarizable electrodes and sulfuric acid as the electrolyte. The AC/C composite was synthesized through a simple process, namely a cured mixture of activated carbon and phenol-formaldehyde resin was carbonized. The AC/C composite has a large surface area, 1300 m2/g, and low resistivity, 0.01 OMEGA . cm. Two kinds of pores exist in the AC/C composite, macropores with submicrometer diameters, and micropores with below 4-nm diameter. A sulfuric acid aqueous solution, as an electrolyte, is impregnated into the micropores through the macropores open to the outer surface. The electric double layer capacitance per unit volume for the AC/C composite in sulfuric acid is greater than that for activated carbon powder as a raw material. The electric double layer capacitor with large capacitance using the AC/C composite is expected to be used as a new energy storage device and a new supplementary power source.